Wall Street closed out another erratic week with a big gain Friday after investors took comments from President Bush and Federal Reserve Chairman Ben Bernanke as reassuring signs Wall Street won’t be left to deal with problems in the mortgage and credit markets on its own.

Investors balked early in Friday’s session when comments from Bernanke – speaking at the Fed’s annual conference in Jackson Hole, Wyo. – didn’t indicate a cut in the benchmark federal funds rate was imminent. However, they later appeared to concentrate on comments that the Fed would step in if needed.

The major indexes fluctuated but by midday extended their gains after Bush spoke about details of a plan to help borrowers facing trouble paying their mortgages.

The Dow rose 119.01, or 0.9 percent, to 13,357.74. The Dow slipped 0.16 percent for the week. The Standard & Poor’s 500 index rose 16.35, or 1.12 percent, to 1,473.99. For the week, the S&P fell 0.36 percent, leaving it with a 3.9 percent gain for the year. The Nasdaq composite index rose 31.06, or 1.21 percent, to 2,596.36. It gained 0.76 percent for the week and is up 7.5 percent for the year.